Method and system for processing waste products generated in an animal dehairing operation

ABSTRACT

Disclosed is a novel method and system for dehairing an animal, providing a system for recycling and safely disposing of chemical and biological wastes produced during such dehairing method. Included in such method are processes for handling sodium production in waste materials, reducing and handling production of H 2 S, removing sulfides from animal hides, safely disposing of sulfide waste, removing solids from the waste materials, and reducing water and reagent use and disposal.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation application of pending prior application No.09/942,163 filed Aug. 28, 2001 now U.S. Pat. No. 6,458,024, which is acontinuation of pending prior application No. 09/769,548 filed Jan. 24,2001, now U.S. Pat. No. 6,322,436 issued Nov. 27, 2001, which is acontinuation of Ser. No. 09/630,450 filed Aug. 2, 2000, now U.S. Pat.No. 6,220,951 issued Apr. 24, 2001, which is a continuation from Ser.No. 09/256,246 filed Feb. 23, 1999, now U.S. Pat. No. 6,129,623 issuedOct. 10, 2000, which claims priority from U.S. Provisional PatentApplication No. 60/075,493 filed Feb. 23, 1998. The entire disclosure ofthe prior applications are considered to be part of the disclosure ofthe accompanying application and are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method and system for the removal ofhair from animals prior to slaughtering of such animal, and to reuse,recycling and disposal systems for compositions generated in such adehairing method.

BACKGROUND OF THE INVENTION

In the meat industry, and particularly in those areas devoted to theprocessing of beef and pork, meat packers slaughter animals in a processin which the animals are stunned, bled, skinned, eviscerated, andfabricated into meat sections which are marketable to the public or therestaurant trade. Animals enter a meat slaughter plant with variousforeign materials present on their hair, including blood, dirt, manure,mud and vegetative material. An animal's hair is also contaminated witha multitude of microorganisms, some of which are pathogenic to humans.Most bacteria present in a meat slaughter and processing facility arecarried into the facility on the hides of animals to be slaughtered.During the slaughtering process, these microorganisms contact meat andother meat by-products, thereby contaminating such products, creatinghandling problems and reducing the shelf life and safety of meatproducts.

The control of contamination by microorganisms is a recognized problemin the meat packing industry. Many techniques have been employed in thepast in an effort to destroy surface bacterial flora on meat. Forexample, U.S. Pat. No. 4,852,216 to Clayton discloses a disinfectionsystem using acetic acid spray in order to reduce bacteria levels andthereby increase shelf life of meat products. Other inventors haveutilized anti-microbial agents for preserving products normally subjectto microbial spoilage. For example, U.S. Pat. No. 3,915,889 to Jurddiscloses a certain anti-microbial agent that can be applied forpreservation of a wide variety of substances including meat by-products.

Still other inventors have recognized the advantages of dehairinganimals to facilitate the slaughtering process. U.S. Pat. No. 4,674,152to Georges discloses an apparatus and method for slaughtering animals bybleeding an animal, electrostatically charging the animal's hair,applying a combustible fluid to the hair and subsequently igniting thecombustible fluid to burn the hair from the animal's body. U.S. Pat. No.4,309,795 to Simonsen discloses a method and apparatus for dehairinghogs wherein the hog is bled, its skin is scalded with hot water andthen subjected to abrasive treatment to remove the hog's hair. U.S. Pat.No. 5,149,295 to Bowling et al., which is incorporated herein byreference in its entirety, discloses the use of a depilatory substanceto remove animal hair, such depilatory substance including a chemicalthat is able to cleave disulfide bonds between cysteine amino acidresidues present in animal hair.

Methods for dehairing which use chemicals to remove animal hair,however, generate chemical and animal byproducts which can be toxicand/or environmentally hazardous and can pose significant problems forwaste disposal. Therefore, a need exists for a method for dehairinganimals which includes protocols for recycling and/or safely disposingof compositions and waste products produced during the process. Thepresent invention addresses such a need by providing a process forreducing bacterial contamination of meat and meat by-products from theoutset of the slaughtering process, prior to the exsanguination of theanimal, while minimizing the cost and environmental impact of such aprocess through a novel recycle, reuse and disposal system.

SUMMARY OF THE INVENTION

The present invention is directed to a method and system for dehairinganimals which includes processes for recycling, reusing and safelydisposing of chemical and biological waste products from such adehairing process. More particularly, the present invention is generallydirected to a process for dehairing an animal, which includes the stepsof immobilizing the animal, prewetting the hide, applying a depilatorysubstance to the hide, removing the hair from the hide, and dispatchingthe animal. In certain embodiments, the present method also includes thesteps of neutralizing the hide and washing the hide with fresh water.Included in each step of this method are collection, recycling and wastedisposal processes for treating individual or combined waste streamsfrom the prewetting, depilatory application, hair removal, neutralizing(if necessary) and fresh water rinse (if necessary) steps. As usedherein, “liquid and/or solid wastes” are meant to include liquid and/orsolid constituents since such liquids and/or solids may be recyclableand thus may not be technically deemed to be “wastes”.

Such processes for waste stream treatment can include the steps of: (a)separation of solid waste from liquid waste; (b) further separation,recycling and-disposal of solid wastes; and (c) treatment and recyclingof liquid wastes. Step (b) of further separation, recycling and disposalof solid wastes can include separation of hair from other solids such asmud and manure, followed by recovery of valuable proteins from the hairand recycling/disposal of mud and manure to land applications orlandfills. Step (c) of treatment of the liquid waste can include any orall of the steps of (a) removing fine solid waste from the liquid; (b)recovering and recycling water from the liquid waste; (c) recovering andrecycling sulfides from the liquid waste; (d) controlling, removingand/or recycling of H₂S gas from the liquid waste; and (e) recycleand/or disposal of residual sulfides in the liquid waste as sulfates.

BRIEF DESCRIPTION OF THE DRAWINGS OF THE INVENTION

FIG. 1 is a flow chart which schematically illustrates a dehairingprocess according to the present invention.

FIG. 2 is a flow chart which schematically illustrates a dehairingprocess according to the present invention.

FIG. 3 is a flow chart which schematically illustrates a dehairingprocess according to the present invention.

FIG. 4 is a flow chart which schematically illustrates a dehairingprocess according to the present invention.

FIG. 5 is a flow chart which schematically illustrates a dehairingprocess according to the present invention.

FIG. 6 is a flow chart which schematically illustrates a chemicalrecycle process according to the present invention.

FIGS. 7A and 7B are schematic illustrations of a screen separation stepaccording to the present invention.

FIG. 8 is a schematic illustration of an apparatus for acid treatment ofsubmitted, spent dehairing liquor for recovery of residual sulfide valuevia H₂S absorption in a caustic soda scrubber.

FIG. 9 is a flow chart which schematically illustrates a process forlaboratory treatment of submitted spent dehairing liquor for recovery ofresidual sulfide value via H₂S absorption in a caustic soda scrubber.

FIG. 10 is a flow chart which schematically illustrates a caustic sodascrubber for H₂S recovery as NaHS.

DETAILED DESCRIPTION OF THE INVENTION

The present invention reduces microbial contamination of meat and meatby-products by removing the hair of an animal before the disassembly ofthe animal during slaughtering, thereby substantially eliminating allforeign matter, including dirt, manure, blood, ingesta and mostimportantly, microorganisms, associated with animal hair. The presentinvention additionally provides a system for effectively recycling,reusing and disposing of chemical and animal products generated by thehair removal process which minimizes the cost and environmental impactof the dehairing method.

More particularly, the present invention provides a novel, comprehensiveanimal hair removal (dehairing) system which addresses various potentialconcerns with the animal hair removal process, including issues relatedto efficient and effective hair removal, sodium production in wastematerials, production of H₂S during the process, elimination orreduction of the use of certain chemicals in the process, removal ofsulfides from animal hides, sulfide waste disposal, removal of solidsfrom the waste materials, and reduction in water and reagent use anddisposal.

In a meat processing facility, the opportunity for microbialcontamination of meat and meat by-products first presents itself uponthe cutting open of an animal, exposing the animal's interior tomicroorganisms present in the ambient environment. The risk of microbialcontamination extends throughout the entire slaughtering process,including final fabrication of the animal into various sections of meatfor commercial sale.

By practicing the present invention, the slaughtering process isinitiated with animal carcasses essentially free of foreign matter andmicroorganisms, with minimal environmental impact. Using conventionalprocedures, animals enter the slaughtering process in a highlycontaminated state and are processed in a manner that permitssignificant meat contamination to occur. In contrast, the depilatoryhair removal method described herein drastically reduces the number ofmicroorganisms from the onset of the slaughtering process, and increasesthe effectiveness of subsequent measures taken in the meat processingprocedure to control the growth of spoilage and pathogenicmicroorganisms.

As used herein, the term microorganism refers to any microorganismscapable of contaminating meat products, thereby making such meatunsuitable or unhealthy for human or animal consumption.

As used herein, the term “animal” refers to any mammal of the kingdomAnimalia which is consumed by humans or animals, including withoutlimitation, bovine, ovine and porcine, and the term “hide” refers to theintegument of an animal, such as a bovine hide, a porcine skin and anovine pelt. The primary function of an animal hide while the animal isalive is to both form a protective barrier to actively prevent thepenetration of material through the animal's hair. Microorganisms areunable to penetrate an intact living animal hide but can begin to enterthe hide immediately upon the death of the animal. For four to eightminutes after an animal is immobilized, its skin continues acting as anactive barrier to microorganisms.

Various embodiments of the method of the present invention areillustrated schematically in the flow charts and diagrams of FIGS. 1-10.The method is particularly described in detail below. Briefly, thedehairing method of the present invention can include the steps of:immobilizing an animal, presoaking the hide, applying the depilatorysubstance to the hide, removing the animal hair from the hide; applyinga neutralization substance to the hide; applying a fresh water rinse tothe hide; dispatching the animal; and various recycling and wastedisposal steps that are integral with each of the above-mentioneddehairing steps. It is to be understood that some of these steps areoptional, and that the particular order and inclusion of steps can bevaried according to the needs and safety concerns of the user of themethod.

The step of immobilizing an animal (e.g., stunning) is preferablyperformed prior to the application of a depilatory substance to theanimal's hide. Immobilization includes any means for precluding movementof the animal. Such methods are described in detail, for example, inBowling et al., U.S. Pat. No. 5,149,295, supra.

One embodiment of the invention further includes contacting a surfactantor wetting agent to the animal either prior to (e.g., a presoaking step)or in conjunction with a depilatory substance. Such a presoaking stepfacilitates the ability of the depilatory substance to go to thefollicle at the surface of the hide, and also facilitates the removal ofthe depilatory substance from the hide later in the process. Penetrationof the depilatory substance to the surface of the hide, and morepreferably, below the surface of the hide and into the hair follicle canreduce the amount of dwell time for the depilatory substance on thehide, thereby improving throughput. Surfactants and wetting agentsmodify the nature of a surface and are known to break the surfacetension of water, thus allowing for increased saturation of chemicalsapplied subsequent to or in conjunction with such surfactants andwetting agents. The surfactant or wetting agent of the present inventioncan be any composition known to those skilled in the art suitable forincreasing penetration of depilatory substances on the hair of ananimal. Preferably, the surfactant or wetting agent is chemicallycompatible with the depilatory substance to be used. For example, whenused in the presoaking step of the present invention, a suitablesurfactant or wetting agent facilitates the penetration of thesubsequent depilatory substance close to the surface of the hide whileminimizing chemical reactions with the depilatory substance that produceundesirable and/or toxic byproducts.

More particularly, surfactant or wetting agents include soaps, alcohols,fatty acids or detergents, preferably sodium salts of fatty acids, andmost preferably sodium lauryl sulfate. In one embodiment of the presentinvention, the wetting agent used in a presoaking step can be liquidthat has been recycled from the presoaking and/or depilatory applicationsteps. Such recycled wetting agents can be applied with or without asurfactant.

The amount of surfactant used in a particular application depends on thestrength of the depilatory substance used, the condition of an animal'shair, the temperature of the depilatory substance, and the amount ofdepilatory substance contact time, among other factors. Typically, thesurfactant, when applied in connection with the depilatory substance, isapplied in amounts by volume percent of depilatory substance of betweenabout 3.0% and about 0.1%, more preferably between about 2% and about0.3%, and most preferably between about 0.7% and about 0.4%. In a beefprocessing operation, for example, a single hide may be presoaked withabout 50 gallons of wetting agent.

The step of contacting or applying the depilatory substance to an animalcan involve any method which sufficiently contacts a depilatorysubstance with the hide of an animal to allow the depilatory substanceto react with the animal's hair. Such methods may include, but are notlimited to, immersing, spraying, showering or dousing of the animal, orany other means known in the art for applying similar substances to ananimal or animal hide. Preferably, the step of contacting or applyingthe depilatory substance to an animal is any method which facilitatesthe penetration of the depilatory substance to the hair follicle at thesurface of the animal's hide. In a further embodiment, the step ofcontacting or applying is any method which facilitates the recovery andcollection of residual depilatory substance for reuse and/or recycling.Particularly preferred methods of contacting or applying includespraying and immersion. In one embodiment of the present invention, theprewetting solution used to prewet one hide is collected and reused(e.g., recycled) to prewet another hide.

In one embodiment of the present method, a depilatory substance isapplied to an animal hide in two steps. The first step comprisesspraying the depilatory substance onto a preheated hide under lowpressure, followed by a second application of the depilatory substanceusing a high pressure spray. Preferably, the spraying apparatus whichdelivers the depilatory substance is comprised of several moveablenozzles arranged around the hide in such a configuration that allsurfaces of the hide are contacted with the spray, including areas whichmay be more difficult to contact, such as the area between the body anda leg of the animal. In this embodiment of the present invention, thesubstances used in the prewetting and low pressure application can beeither fresh prewetting and depilatory substances, or more preferably,are recycled from previous prewetting and low pressure depletion ofhides. Preferably, the depilatory substance used in the high pressureapplication is freshly made depilatory substance, although componentsrecycled from various steps of the dehairing process can be used to makeup the depilatory is substance.

In the embodiment of the present invention wherein the hide is immersedin a depilatory substance, the animal is typically lowered into a bathof prewetting and/or depilatory substance. In this embodiment, it ispreferable to provide a means of supporting the animal head above thebaths such that the orifices of the animal's head (e.g., the eyes, nose,ears and mouth) do not contact the prewetting or depilatory substances.Such a supporting means can be any suitable device which functions tohold the animal head above the level of the bath during theimmersion/dipping process. It is important to avoid internal contact ofthe animal with the chemicals used in the dehairing process to preventcontamination of the meat that is to be harvested from the animal laterin processing.

In another embodiment, a depilatory substance is left to dwell on theanimal hide until the hair is cleaved a small distance below the surfaceof the hide and the upper epidermis is removed. In an embodiment usingsodium sulfide as the depilatory substance, the depilatory substance issprayed onto the animal's hide for 1-60 seconds and left to dwell for anadditional 1-180 seconds. In an embodiment using potassium sodiumsulfide as the depilatory substance, the depilatory substance is sprayedonto the animal's hide for between about 5 to about 25 seconds and leftto dwell for an additional time period of between about 20 to about 200seconds.

As discussed above, the depilatory substance is preferably sprayed ontothe animal's hide using a spray apparatus comprised of a plurality ofmoveable nozzles which are configured around the hide such that theentire surface area of the hide is contacted with the depilatorysubstance.

In a preferred embodiment of the present invention, the prewetting anddepilatory application steps are designed to maximize the contact of thedepilatory substance with the hair follicle at the surface of the hide,and more preferably, with the follicle below the surface of the hide.Such contact will allow the hair to be removed below the surface of thehide and is preferable to cleavage of the hair above or at the surface,which leaves “hair stubble” on the hide. Hair stubble is undesirablebecause such hides have increased risk of microbial contamination andhave decreased value to tanners. In addition, a smooth hide facilitatesthe removal of the depilatory substance from the hide later in theprocess.

The depilatory substance of the present invention is any chemicalcompound known to depilate hair from an animal's hide. While notintending to be bound by theory, it is believed that depilatorysubstances remove hair by breaking chemical bonds within individual hairfibers. Animal hair, and specifically cattle hair, is composed primarilyof a single structural protein, keratin. Individual keratin moleculesare held together to form hair fibers by covalent disulfide bridgesbetween cystine amino acid residues. These bonds are easily broken byreducing chemicals. Under strong reducing conditions, most of thedisulfide bonds in a hair fiber will be broken and the hair will becleaved into pieces less than a few millimeters in length. Otherdepilatory substances, such as strong caustic agents, act by oxidizingchemical bonds within hair fibers. An example of such caustic agents isa solution comprising sodium hydroxide, further described below.Therefore, according to this theory, the depilatory substances used inthe present invention dissolve certain portions of an animal's hair andpermit removal of the hair from the animal's hide. Moreover, uponcontacting of a depilatory substance to an animal's hide, manymicroorganisms are initially killed by the strong reducing and oxidizingagents utilized.

It is within the scope of the present invention that the selection ofthe depilatory substance and the dwell time of the depilatory substanceon the animal hide can be varied according to whether it is desired: (1)to remove the hair particle by breaking the hairs into small pieces andcollecting the pieces for further use or processing, or alternatively,(2) to actually dissolve the hair, portions of the follicle, and othercomponents on the surface of the hide to form a mush comprised ofmultiple compositions.

Preferably, the depilatory substance of the present invention can besodium sulfide or potassium sodium sulfide; a composition ofthioglycolic acid, sodium hydroxide and calcium oxide; sodium hydroxideand hydrogen peroxide; or potassium hydroxide and hydrogen peroxide.Care should be taken to use the various depilatory substances inamounts, concentrations and contact times which do not damage the animalhide. When the depilatory substance comprises sodium sulfide, sodiumsulfide is in a concentration from about 5% to about 15%, morepreferably from about 8% to about 13%, and most preferably from about 9%to about 12%. When the depilatory substance comprises potassium sodiumsulfide, potassium sodium sulfide is in a concentration from about 5% toabout 20%, more preferably from about 10% to about 15%, and mostpreferably from about 11% to about 14%.

In the embodiment of the invention in which the depilatory substancecomprises sodium hydroxide and hydrogen peroxide, NaOH is present in aconcentration of about 10% to about 20%, more preferably about 12% toabout 17%, and most preferably about 13% to about 15%. In thisembodiment, hydrogen peroxide is present in a concentration of about 1%to about 10%, more preferably about 2% to about 8% and most preferablyabout 4% to about 6%. In the embodiment of the invention in which thedepilatory substance comprises potassium hydroxide and hydrogenperoxide, KOH is present in a concentration of about 10% to about 20%,more preferably about 12% to about 17%, and most preferably about 13% toabout 15%. In this embodiment, hydrogen peroxide is present in aconcentration of about 5% to about 15%, more preferably about 7% toabout 13% and most preferably about 8% to about 12%.

In another embodiment of the invention, the depilatory substancecomprises about 5% to about 15% thioglycolic acid, about 1% to about 5%calcium oxide and about 1% to about 5% sodium hydroxide. It is morepreferable in the above embodiment to have thioglycolic acid in aconcentration of about 7% to about 12%, and most preferably in aconcentration of about 8% to about 11%.

In addition to the foregoing specific formulations, other chemicalsrecognized in the art as effective to remove or dissolve hair from thehide of an animal, can be used as well.

It has been recognized that certain depilatory substances work moreeffectively when heated, specifically, the above described depilatorysubstance comprising sodium hydroxide and hydrogen peroxide and thosecomprising thioglycolic acid, calcium oxide and sodium hydroxide. It ispreferable to heat the respective depilatory substances to a temperaturebetween about 90° F. and about 190° F., although to minimize deleteriouseffects on the animal hide, the depilatory substance is preferablyheated to a temperature that is less than about 120° F., and morepreferably, between about 90° F. and about 120° F. The dwell time of anyparticular depilatory substance contacted with an animal's hide willvary depending upon the particular animal species, the type andconcentration of depilatory substances used and the temperature at whichsuch depilatory substances are applied, as well as other factors. In apreferred embodiment using sodium sulfide, the depilatory substance iseffective at about room temperature.

It is also desirable to maintain the pH of the depilatory substancerelatively high (e.g., about 8 to about 13 pH, and more preferably,about 10 to about 13.5 pH), since a higher pH enhances the depilatoryreaction and reduces the production of undesirable gases during theprocess. For example, when sodium sulfide is the depilatory substance,care must be taken to keep the pH level of the depilatory substancerelatively high (about 9.5 to about 12) so as to avoid excessiveproduction of hydrogen sulfide gas (H₂S) which is deadly poisonous. Inone embodiment of the present invention, the pH of all of the substancesused in the dehairing process is maintained throughout the process at apH greater than about pH 10, and more preferably, greater than about pH11. The present inventors have discovered that maintenance of a veryhigh pH throughout the dehairing process greatly enhances the removal ofhair from the animal hide and prevents the formation of H₂S gas duringthe process. Moreover, due to the effectiveness of the recycling andwaste disposal steps discussed below, the present method can be used, insome embodiments without the need for a neutralizing step.

The step of removing hair in the present invention can be accomplishedin any manner which substantially eliminates the majority of hair on theanimal. The dehairing of animals is performed relatively quickly tofacilitate the timely conveyance of such animals along a meat processingline. In a preferred embodiment, hair is removed from an animal bydirecting pressurized water at the animal. The pressurized jets of watereffectively strip the loosened hair from the animal's hide withoutdamaging the hide. Other embodiments of the present invention includemeans for removal of hair using mechanical devices such as rigid blades,brushes or combs. Pressurized air sprays can also be effective inremoving hair from the animal, especially in conjunction with the use ofpressurized water sprays. The removal of the hair and microorganismsassociated with such hair, achieves the objective of reducing microbialcontamination of meat and meat by-products during the remainder of theslaughtering process.

In an alternative embodiment of the invention, a neutralizing substancecan be applied to an animal subsequent to contacting a depilatorysubstance to the animal, and typically subsequent to the removal of thehair from the animal, although such a neutralizing step can be performedprior to the hair removal step. The neutralizing substance is providedto cease the particular chemical action of the depilatory substance. Useof a particular neutralizing substance depends upon the depilatorysubstance being used. For example, in one embodiment of the presentinvention, the depilatory substance sodium sulfide is neutralized byapplication of sodium bicarbonate or sodium carbonate in combinationwith hydrogen or sodium peroxide. In this embodiment, about 5% to about15% sodium sulfide is applied to the animal's hide and left to dwell forabout 1 to about 180 seconds before removal of the animal's hair. Afterremoval of the hair, a solution containing about 5% to about 15% sodiumbicarbonate and about 1% to about 5% peroxide is sprayed onto theanimal's hide and left to dwell on the hide for about 1 to about 60seconds to allow for the oxidation of sulfide ions. Additional peroxideapplications may be used for complete oxidation of any remainingsulfides. Such additional applications of peroxide may be followed byadditional carbonate and sodium bicarbonate washings to further adjustpH levels.

In another embodiment of the present invention using a combination ofsodium hydroxide and peroxide as the depilatory substance, an oxidatingagent such as an organic acid, for example, acetic acid, propionic acid,lactic acid or citric acid, is used to cease the depilatory action ofthe depilatory substance. When a composition of thioglycolic acid,sodium hydroxide and calcium oxide is used as the depilatory substance,hydrogen peroxide is used as the neutralizing substance. The amount ofneutralizing substance used in a particular case depends upon the amountand type of depilatory substance used, the time constraints on thedehairing process, as well as other factors.

As discussed above, the neutralizing step of the present invention isoptional. It is an advantage of the present invention that the recyclingand waste disposal steps described below are sufficient to reduceproblems associated with production of toxic H₂S gas and the removal andhandling of sulfides from the hides, so that additional neutralizationsteps may not be necessary. In addition, elimination of such aneutralization step further reduces waste disposal issues associatedwith the neutralization liquors.

In a further embodiment, the method of dehairing an animal of thepresent invention can include a fresh water rinse which is performedafter the removal of the hair and/or the neutralizing step and prior tothe dispatching of the animal.

The additional step of dispatching of an animal is preferably performedsubsequent to the step of removing hair from an animal. The term“dispatch” as used herein refers to the killing of the animal and istypically accomplished by exsanguination of the animal through thesevering of the animal's carotid artery while the animal is immobilizedand suspended from a conveyor line.

Having described the initial steps in the method of the presentinvention for dehairing an animal, the description now turns to thesecond and integral portion of the method, a novel system forcollecting, recycling, reusing, and/or disposing of the variouscompositions and byproducts of the above described process. As discussedabove, this embodiment of the method of the present invention offersmany advantages and improvements to the dehairing system, since such amethod increases the cost effectiveness and reduces the negativeenvironmental impact of the above-described dehairing process. While thesecond portion of the method is described as it would be used with thedepilatory substances particularly described herein, the method can beeasily adapted for use with other depilatory substances. It is to beunderstood that eliminating or varying particular steps of the presentmethod according to the needs and facilities of the individual user isintended to be encompassed within the scope of the present invention.

In the recycling/disposal embodiment of the method of the presentinvention, the sludge by-product produced by the dehairing process iscollected along with the presoaking substances, depilatory substances,surfactants, neutralizing substances, and various foreign matter foundin the hair. These substances are sent through various recycling andcleansing/disposal processes as described below. Hair recovered andseparated from the sludge can be further processed for use as animalfeed and for composing of fertilizer precursors, as well as other usesincluding recovery of specific amino acids.

In the total method for dehairing an animal of the present invention,after each step, a waste stream is produced. It is within the scope ofthe present invention that each of these waste streams can beindividually collected and treated, collected and treated in smallgroups, or collected and treated as a single waste solution. In oneembodiment, it may be preferable to collect each of the waste streamsindividually to maximize the recycling and reuse of various components.Such collection may be accomplished, for instance, by collecting a wastestream from each step through a drain on the floor of the area whereeach step is performed (or from individual basins if immersion is used),and routing the waste streams individually to various treatment areas.For example, it may be desirable to separate the waste stream of theprewetting step and/or low pressure depilatory application step from thehigh pressure depilatory application step or immersion depilatoryapplication step in order to facilitate the separation of manure/mudwaste (from the prewetting/low pressure steps) from the hair waste (fromthe high pressure/immersion step). In addition, as will be apparent fromthe discussion below, the present invention includes a novel process forrecycling various chemicals used in the depilatory process, andefficiency of such recycling steps may be increased by disposing ofdifferent waste products separately. Moreover, as will be discussedbelow, it may be desirable to recycle some waste products after onlyminimal treatment, while other waste streams will require more complexwaste treatment before recycling is possible.

In another embodiment, the waste streams can be collected and treatedtogether, such as through a plurality of floor drains or basin drainswhich feed into a common recycling/treatment facility.

One embodiment of the system for recycling and waste disposal isschematically illustrated in the flow diagrams of FIGS. 1-6. Particularembodiments of such a system are described in detail below.

In one embodiment of the present invention, the liquors from thepresoaking, depilatory application, hair removal, neutralizing, and/orfresh water rinse steps, which contain the various applied substances,hair, manure and other solids, are collected (separately, in smallgroups or as a single waste stream) and initially sent (separately, insmall groups or as a single waste stream) through a system and/orsystems for separating liquids from solids. Such a system can be anysystem for achieving such separation and can include centrifuges and/orscreening devices. Additionally, the waste stream collected from theneutralizing rinse and/or the fresh water rinse (i.e., after removal ofthe animal hair) can be recycled back to the neutralizing substancemakeup system for reuse.

In the embodiment illustrated in FIGS. 1-5, large particle solids areseparated from the liquor by use of a Parkson Traveling Belt Screen anda series of vibrating screens of increasing mesh size. For example, thewaste material can be passed from the Parkson Traveling Belt Screen,which is a continuously moving belt or plate filter screen, to a screenhaving a pore size opening of between about 0.1 to about 0.4 inches. Oneembodiment of the screen separation step is specifically illustrated inFIG. 7. In this figure, the used mother liquor is poured onto the top ofa screen of about 3-6 mesh which is mounted at a 45-60° slope. Thescreen can be, for example, a wire screen which is framed in wood,having a hydrophobic manmade woven or knit cloth mounted on the screen.The solids stay on top of the screen, rolling down into a collectiontrough, while the screened liquor is collected in a drain pan fortransport to the next separation/purification step. A 40 micron screen,and then a 10 micron screen can be used to further separate solidcomponents.

The solids collected from the screening separation processes can be sentto a solids separation system to separate the animal hair from othersolids, such as mud and manure. Separated mud and manure can berecovered and used in a fertilizer product, or alternatively, the mudand manure can be used in a land application or sent to a landfill fordisposal. Hair separated at this stage can be sent to a hair proteinrecovery process, where the recovered proteins (i.e., amino acids) aremarketed for use in other applications.

At this stage, some of the liquor from the initial solids separationstage can be recycled back to be reused in the presoaking and/or initialdepilatory application steps, if desired. The remainder of this liquorpasses from the screening processes through an optional centrifugesystem, which will remove finer impurities from the liquor. For example,in one embodiment, the liquor moves from the screening system intohorizontal centrifuges, and then to vertical centrifuges. The wastecollected from the centrifuge system can then be sent back to the solidsseparation system as discussed above and/or directly to a landapplication or landfill.

In the next step of the recycling/disposal process, the liquor passesfrom the centrifuge system to a bag filter system. Alternatively, it maybe desirable and sufficient to eliminate the centrifuge system stepaltogether and move directly from the screening system to the bag filtersystem. The bag filter system is comprised of a series of bag filtershaving decreasing pore size through which the liquor passes. Forexample, the liquor can move from the centrifuge system to a series of10 micron bag filters, and then to a series of 2 micron bag filters. Inthis step, solid waste filtrate from the bag filters can be sent to thesolids separation system as discussed above, and/or directly to a landapplication or landfill.

In the next step of the recycling process, the filtered liquor movesfrom the bag filter system to a reverse osmosis system. In this system,external pressure is applied to the filtered liquor to oppose thenatural process of osmosis, forcing the water in the liquor out of theliquor, which is high in salts. In one embodiment-of the presentinvention, the reverse osmosis system is a two phase system. A reverseosmosis system will typically recycle about 70% of the liquor flow asrecycled water and will waste about 30% of the liquor flow. Preferably,the recycled water produced by this system contains less than about 20ppm of dissolved solids. The recycled water can be adjusted to a neutralpH (i.e., about 7), if necessary, and recycled to the depilatorysubstance or neutralizing substance makeup systems (i.e., the systemswherein these substances are diluted and mixed prior to theirapplication to the hides). In a preferred embodiment of the presentmethod, the recycled water is not neutralized to pH 7, since productionof a depilatory substance having a high pH is preferable, and sinceelimination of the neutralization substance can be accomplished due tothe recycling steps set forth herein.

The waste from the reverse osmosis process will contain a highconcentration of chemicals and byproducts from the hair removal process.The next steps of the method of the present invention are designed todispose of this waste in a safe and efficient manner. First, the wastefrom the reverse osmosis process moves to a salvaged chemical recyclingprocess. This process will salvage chemicals such as sulfides from thewaste, allowing the sulfides to be recycled back to the depilatorymakeup system. Briefly, in the salvaged chemical recycling processwherein the chemicals include sulfides and sulfates, the waste, or spentliquor is transferred to a totally enclosed, air-tight vessel. An acid,such as HCl, can then be added to the spent liquor, which, under lowerpH conditions, can generate H₂S gas. The H₂S gas can be collected andscrubbed by passage through a caustic soda scrubber, an embodiment ofwhich is illustrated in FIGS. 8, 9 and 10. More particularly, the H₂Sgas generated by the reaction of sulfides and acid is collected in acontained system which heats, concentrates and releases the sulfide intoa sodium hydroxide or potassium hydroxide solution. The concentratedsulfide solution can then be pumped into a storage system for reuse, forexample, in the depilatory makeup process. The air in the system canthen be safely released into the atmosphere.

At this stage, the remainder of the waste liquor can be sent to a wastechemical treatment and disposal process. In this process, the collectedwaste solution from the above-described chemical salvage process is heldin an air-tight vessel and the pH is adjusted, if necessary, to about10.5 to stabilize the liquor and reduce the potential for hydrogensulfide gas release. As discussed above, it is a preferred embodiment tomaintain the pH at greater than pH 10 throughout the process, therebyeliminating the need to adjust the pH at various recovery steps. Oxygenis then added to the solution by the addition of ozone, hydrogenperoxide, or any other suitable oxygenation method. In addition, lime isadded to the liquor. The addition of oxygen to the liquor changes theresidual sulfides in the liquor into sulfates, and the addition of limeprecipitates the sulfates out of the liquor in the form of calciumsulfate. The precipitated solids can then be removed from the solutionby any suitable method, such as by centrifugation. Preferably, thecalcium sulfate solids are removed by three phase horizontalcentrifugation. The calcium sulfate solids can then be transported to aland application and/or landfill sites. The final remaining liquid wastesolution can now be safely transported to a wastewater treatmentfacility for discharge, or to a Class I disposal well.

Still another aspect of the present invention relates to the use ofpotassium-based-compounds to supplant the amount of sodium-basedcompounds used in the dehairing process. In such a manner, the problemsassociated with the recovery and recycling of sodium is decreased, ifnot eliminated. For example, the use of potassium hydroxide and sodiumhydroxide in a mixture, preferably about 50% of each, more preferably atleast about 40% sodium hydroxide, has been found to reduce the amount ofsodium recovery/recycling problems.

As will be appreciated, another aspect of the present invention isdirected to the system itself for facilitating the above-describedmethod. Such a system includes, for example: a system for removing hairfrom an animal, wherein said animal is immobilized, dispatched andfabricated, said system comprising the steps of:

a. a means for contacting a prewetting substance comprising a surfactantto an animal's hair;

b. a means for contacting a depilatory substance to the animal's hair;and

c. a means for removing the hair contacted by the depilatory substance;

d. a means for collecting a waste stream comprising a prewettingsubstance, a depilatory substance and removed hair; and,

e. a means for processing said waste streams by a system comprising:

1. a means for separating solid waste from liquid waste;

2. a means for treating the solid waste to separate hair from othersolids;

3. a means for recovering protein from the removed hair; and,

4. a means for treating the liquid waste to produce a result selectedfrom the group consisting of: removal and recycling of sulfides, removalof fine solid waste from the liquid; recovering and recycling water fromthe liquid waste; eliminating H₂S gas from the liquid waste; anddisposal of residual sulfides in the liquid waste as sulfates.

In one embodiment, used liquor 20 is provided to a wire screen 22, suchwire screen 22 preferably bounded by a frame, such as a wooden frame 24.Such wire screen's dimensions are preferably at least about 2 squareyards in an area and is preferably mounted at a 45°-60° sloped angle.The wire screen 22 preferably has a mesh of between 3 and 6 with ahydrophobic man-made woven or knit cloth having openings of at leastabout 0.04 inches. Positioned beneath the wire screen 22 is a drain pan26 for the screened mother liquor. Shown in FIGS. 7A and 7B are views ofthe above-described screening process.

With respect to FIG. 8, an apparatus for acid treatment of spentdehairing liquor is provided so that residual sulfide can be recoveredand H₂S absorbed in a caustic soda scrubber. As illustrated, a droppingfunnel containing HCl 32 is connected to a resin flash 34 which iscontained within a heating mantle 36. A stirrer bar 38 is used toagitate the spent liquor 40 by means of a magnetic stirrer 42. Themantle 36 is connected to a variac 44. A thermal well 46 is connected toa thermal couple 48, such thermal well 46 immersed in the spent liquor40. A nitrogen purge 50 is connected to and in contact with the spentliquor 40 within the resin flask 34. The top of the resin flask 34 isconnected to at least one caustic soda scrubber 52 which are ultimatelyvented to the atmosphere 54.

FIG. 9 illustrates an acid treatment of submitted spent, dehairingliquor for recovery of residual sulfide values via H₂S absorption in acaustic soda scrubber.

With reference to FIG. 10, H₂S from acidified spent dehairing liquor istransported so that it comes into contact with 25% NaOH 58 and is pumpedthrough a heater 60 by a typical pump means or a blower 64, ultimatelyconveying material to a thermal oxidizer 66 or to an NaHS storage tank68.

In summary, the method for dehairing animals as disclosed herein is acomprehensive, efficient and cost effective method for removing hairfrom animal hides, while recycling and/or safely disposing ofcompositions and waste products produced during the process.

While various embodiments of the present invention have been describedin detail, it is apparent that modifications and adaptations of thoseembodiments will occur to those skilled in the art. However, it is to beexpressly understood that such modifications and adaptations are withinthe scope of the present invention.

What is claimed:
 1. A method for removing hair from a bovine animal,wherein said animal is immobilized, dispatched, and fabricated, saidmethod comprising the steps of: a) contacting a depilatory substance tosaid animal's hair; b) removing said hair contacted by said depilatorysubstance; c) collecting waste streams from said step (a) of contactingand from said step (b) of removing, wherein said waste stream arecollected separately or together; d) processing said waste streams byseparating solid waste from liquid waste and treating at least one ofsaid waste streams to allow at least one of said waste streams to berecycled; and e) eliminating H₂S gas from said liquid waste and disposalof residual sulfides in said liquid waste as sulfates.
 2. The method ofclaim 1 wherein said liquid streams contain substantially no water. 3.The method of claim 1 further comprising the directing one or more ofsaid waste streams through a separation device selected from the groupconsisting of a centrifuge, a vibrating screen and a screen havinghydrophobic material associated therewith.
 4. A method for removing hairfrom an animal, wherein said animal is immobilized, said methodcomprising the steps of: a) contacting a prewetting substance comprisinga surfactant to said animal's hair; b) contacting a depilatory substanceto said animal's hair; and c) removing said hair contacted by saiddepilatory substance; d) collecting a waste stream from said step (a) ofcontacting, from said step (b) of contacting, and from said step (c) ofremoving, wherein said waste streams are collected separately ortogether; e) processing said waste streams by separating solid wastefrom liquid waste and treating said waste streams, said processing stepfurther including removing fine solid waste from said liquid waste,recovering and recycling water from said liquid waste after removal ofsaid fine solid waste and removal of residual sulfides in said liquidwaste as sulfates.
 5. A method for removing hair from and animal, asclaimed in claim 4, wherein the animal is a bovine, porcine, or ovine.6. A method for removing hair from and animal, as claimed in claim 4,wherein steps a), b) and c) of contacting a prewetting substance,contacting a depilatory substance and removing said hair, are completewithin a time range of around 1 to around 10 minutes after the time fromwhich the animal is immobilized.
 7. A method for removing hair from andanimal, as claimed in claim 4, wherein steps a), b) and c) of contactinga prewetting substance, contacting a depilatory substance and removingsaid hair, are complete within a time range of around 4 to around 8minutes after the time from which the animal is immobilized.
 8. A methodfor removing hair from an animal, as claimed in claim 4, furthercomprising dispatching and fabricating the animal once the animalcompletes steps a), b) and c).
 9. A system for removing hair from ananimal and processing waste streams generated thereby, comprising: a) ameans for contacting a prewetting substance comprising a surfactant tosaid animal's hair; b) a means for contacting a depilatory substance tosaid animal's hair; c) a means for removing said hair contacted by saiddepilatory substance; d) a means for collecting a waste stream; and, e)a means for processing said waste streams by a system comprising: i) ameans for separating solid waste from liquid waste; ii) a means fortreating said solid waste to separate said hair from other solids; andiii) a means for treating said liquid waste to produce a result selectedfrom the group consisting of: removal and recycling of sulfides, removalof fine solid waste from said liquid; recovering and recycling waterfrom said liquid waste; eliminating H₂S gas from said liquid waste; anddisposal of residual sulfides in said liquid waste as sulfates.
 10. Amethod for collecting by products of an animal dehairing process,comprising the steps of: a) collecting a waste stream produced by apre-wetting step, said pre-wetting step comprising contacting a bovinewith a pre-wetting liquid to improve the ability of a depilatorysubstance to contact said bovine's hide; b) collecting hair waste fromhair removed from said bovine animal due to the application ofdepilatory substance to said bovine's hide, said step of collecting hairwaste performed separately from said step of collecting said wastesteam; c) recycling the liquid collected in step (a) and directing it toa station where said pre-wetting liquid is applied to said bovineanimals; d) directing the waste stream from step (b) through aseparation device selected from the group consisting of centrifuge, avibrating screen and a screen having hydrophobic material associatedtherewith, to produce a screened liquor and a separated solid component;e) directing said separated solid components to a separation system toseparate bovine animal hair from other solids selected from the groupconsisting of mud and manure; f) directing at least a portion of saidscreened liquor through at least one centrifuge to remove fineimpurities from said screened liquor, thereby producing a centrifugedliquid; g) directing said centrifuged liquid to one or more bag filtersto produce a bag filtered liquid; and h) directing said bag filteredliquid through a reverse osmosis system whereby at least a portion of aliquid remaining after being directed through said reverse osmosissystem contains less than about 20 ppm of dissolved solids, said reverseosmosis system also generating chemical waste components selected fromthe group consisting of sulfides and sulfates.
 11. The method as setforth in claim 10, further comprising adjusting the pH of said liquidremaining after being directed through said reverse osmosis system. 12.The method as set forth in claim 10, further comprising conveying saidchemical waste components into an enclosed vessel and adding an acidthereto in order to generate H₂S gas, said H₂S gas being collected andscrubbed by passage through a caustic soda scrubber.
 13. The method asset forth in claim 10, further comprising collecting a waste solutionafter said liquid has passed through said reverse osmosis system andadjusting the pH of said waste solution to reduce the potential forhydrogen sulfide gas release.
 14. The method as set forth in claim 13,wherein said pH is adjusted to above about pH
 10. 15. The method as setforth in claim 10, further comprising adding oxygen to said liquidremaining after being directed through said reverse osmosis system inorder to change residual sulfides therein into sulfates and thereafteradding lime in order to precipitate sulfates in the form of calciumsulfate.